What initiates chemical intolerance?

Toxicant-induced loss of tolerance (TILT) is a two-stage disease mechanism that includes initiation, in which a chemical exposure leads to onset of TILT, and triggering, in which subsequent exposures to a variety of chemicals elicit symptoms. Little is known about initiating events and underlying causes of TILT. This analysis reviews several major exposure events that initiated TILT. Examining these events collectively enables a better understanding of the exposures that may initiate TILT, in turn informing exposed individuals, physicians, and policymakers on how best to protect health.